1. Field of the Invention
The present invention relates to an improvement for an impeller of an axial flow type blower to be used in various OA (office automation) equipment, etc.
2. Description of the Related Art
Various OA equipment, such as a computer and a copy machine, are designed to accommodate a large number of electronic parts in a housing, so that the heat generated therefrom is large and may thermally damage the electronic parts. For this reason, an axial flow type blower is mounted to a ventilation hole provided to the equipment housing to release the internal heat out of the equipment.
A typical blower of this type will be described by taking as an example an axial flow type blower driven by an outer rotor type motor with reference to FIG. 9.
As illustrated, a shaft 4 is inserted into and rotatably supported by a central tubular portion 1a of a casing 1 through bearings 2 and 3.
This shaft 4 is attached to a central portion of an impeller 5 (a central portion of a cup portion 5a) that is made up of the cup portion 5a (a tubular portion having a bottom) and a plurality of blades 5b on the outer periphery thereof.
A motor yoke 6a is molded to an inner periphery of the cup portion 5a, and a ring-like permanent magnet 6b is fixed to the inner periphery of the motor yoke 6a. This permanent magnet 6b forms, in cooperation with the motor yoke 6a, a major construction of a rotor (an outer rotor) 6.
A stator 7 is fixed to an outer side of the tubular portion 1a, which has a stator core 7a and a stator coil 7b that are confronted with the permanent magnet 6b. A PC board 8 is attached to a lower portion of the stator 7, and electric circuits are mounted on the PC board 8 to supply a prescribed electric current to the stator coil 7b and to allow the stator 7 and the rotor 6 to serve as a stator and a rotor of a brush-less DC motor, respectively.
The stator coil 7b and the electric circuits on the PC board 8 are connected to each other through a pin 9. A lead wire 10 is connected to the PC board 8.
In the blower constructed as mentioned above, when a prescribed DC voltage of a power source is applied to the lead wire 10, a current controlled by the electric circuits on the PC board 8 is allowed to flow through the stator coil 7b. This generates magnetic flux flow from the stator core 7a to rotate the rotor 6 about the shaft 4 through mutual magnetic effect with respect to magnetic flux flow of the permanent magnet 6b, thereby making the impeller 5 integral with the motor yoke 6a of the rotor 6 rotate for ventilation.
In most cases, the impeller 5 is molded from synthetic resin, and FIGS. 10 and 11 are a rear view and a partially sectional, left side view of a rotor portion, respectively, picked up from an axial flow type blower provided with such impeller 5. In each of figures, components identical to or corresponding to the components shown in FIG. 9 are denoted by the same reference numerals, and the detailed description thereof is omitted.
In a case where the impeller 5 of the axial flow type blower is molded from synthetic resin, metal dies are designed to be axially coupled to each other. For this reason, in view of a molding requirement, blades 5b are disposed at equal angular spacing on the outer periphery of the cup portion 5a so that adjacent two blades 5b and 5b are not overlapped with each other as viewed in the axial direction of the impeller 5 as shown in FIG. 10.
There is a case, however, that the axial flow type blower of this type is required to have an impeller in which adjacent blades 5b and 5b are overlapped with each other as viewed in the axial direction of the impeller 5 in order to, for example, increase a static pressure or the like.
However, with the prior art, such an impeller 5 can not be manufactured from synthetic resin easily and in a cost-effective manner in view of the molding requirement, and a solution on this point was desired.
The present invention has been made in view of the above problems, and an object thereof is to provide an impeller for an axial flow type blower, which can easily and cost-effectively realize an arrangement in which adjacent blades are overlapped with each other as viewed in the axial direction even if the impeller is molded from synthetic resin.
In order to attain the above-noted object, a first aspect of the present invention is directed to an impeller for an axial flow type blower driven by an outer rotor type motor which is integrated to a rotatably supported shaft and a motor yoke to be rotated about the shaft around an outer side of a stator together with the motor yoke for ventilation, the impeller for an axial flow type blower characterized by comprising divided impellers that are molded from synthetic resin separately from and independently of each other, the divided impellers being disposed in series forming multiple stages in an axial direction of the shaft.
In the first aspect of the present invention, divided impellers are separately molded and the divided impellers are then disposed in series forming multiple stages to thereby constitute the impeller as a whole.
Consequently, each of the divided impeller can be molded while satisfying the molding requirement if adjacent blades are set not to be overlapped with each other as viewed in the axial direction.
If all of the divided impellers are disposed in series as multiple stages in the axial direction of the shaft, an impeller obtained as a whole can be provided with adjacent blades overlapped with each other to function as a single impeller. Further, such an impeller can also be obtained, that has adjacent independent blades not overlapped with each other and that has blades in the front stage and the rear stage. That is, the impeller can serve as an impeller having a plurality of blades that are disposed in the axial direction.
According to a second aspect of the present invention, there is provided an impeller for an axial flow type blower of the first aspect of the present invention, in which, of the plurality of divided impellers adjacent to each other in the axial direction of the shaft on the front and rear sides, a front side divided impeller has back end portions of ventilating surfaces which respectively abut against fore end portions of ventilating surfaces of a rear side divided impeller. With this arrangement, a single ventilating surface is formed by the ventilating surface of the front side divided impeller and the ventilating surface of the rear side divided impeller to have a dimension summed up by these surfaces. The impeller constructed thus serves as the aforementioned impeller in which the adjacent blades are overlapped with each other.
According to a third aspect of the present invention, there is provided an impeller for an axial flow type blower of the first aspect of the present invention, in which, of the plurality of divided impellers adjacent to each other on the axial direction of the shaft on the front and rear sides, a front side divided impeller has back end portions of ventilating surfaces which are respectively offset, about the axis, from fore end portions of ventilating surfaces of a rear side divided impeller. The impeller constructed thus serves as the aforementioned impeller in which the adjacent blades are not overlapped with each other, and the independent blades (ventilating surfaces) are provided on the front and rear sides.